1. Field of the Invention
This invention generally relates to a bicycle sprocket. More specifically, the present invention relates to a bicycle sprocket comprising a metallic element and a non-metallic element, with the bicycle sprocket being configured to be mounted to a rotational drive unit such as a crank of a bicycle.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle sprocket.
A bicycle is generally provided with a drive unit or drive train having one or more front sprockets and one or more rear sprockets with a chain wrapped around the sprockets. The front sprocket(s) is provided on the gear crank of the bicycle and the rear sprocket(s) is provided on the free hub of the bicycle. This type of bicycle sprocket is usually made of materials such as aluminium or iron. When several sprockets are mounted to the gear crank or the free hub in order to provide multiple gears, aluminium is preferably used as the material in order to reduce the weight.
There are also known bicycle sprocket designs to reduce the weight even further by having a sprocket ring part that is made of metal such as aluminium. Such a bicycle sprocket typically includes a sprocket ring part with a plurality of sprocket teeth formed thereon, and a fastening part that is made of non-metallic materials such as carbon fiber material or synthetic resin, attached to the inner circumference of the sprocket ring part and fastened to the gear crank such as, for instance, disclosed in German Utility Model No. 202 18 755 U1.
Further bicycle sprocket devices having a metallic sprocket ring part and a non-metallic inner ring part are disclosed in European Publication No. 1 504 988 and European Publication No. 1 609 714, both aiming to avoid play or looseness as encountered when using a device according to the above mentioned utility model.
The general approach in all of the bicycle sprocket configurations according to the prior art and the most general objective is to save as much weight as possible such that the metallic sprocket ring part is configured to be as small as possible since the non-metallic inner ring part is usually having lighter weight.
Although the bicycle sprockets having a metallic sprocket ring part and a non-metallic inner ring part have proven to be very advantageous in saving weight while still providing sufficient stiffness and rigidity, it has been found that providing a non-movable coupling between those two parts is prone to result in a deterioration of the non-metallic inner ring part when aging and being in constant use. Accordingly, there is a need to improve such bicycle sprocket configuration to avoid the above-mentioned disadvantages.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle sprocket. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.